For textures you can eather make your own in PS if you're good at it or search google for the kind of textures you need. When you find the ones you like just put them in the folder of your map or wherever you keep your stuff and convert then to .tex files by using the editor to do so.

As for the models you eather make them in a different software like blender, Zbrush etc. or you use the Mesh/Model editor inside of SED and make your own models there which is what I prefer. Exept if you are planing on making characters then I definitly suggest using a different software. Good luck!

I don't understand, if using official announcements and whatnot people didn't join in 11 days after the main post, what makes you think all of a sudden a wave of people will come in only because you made a post where the registration date got extended for 9 more days?

Personally I think you should save this contest for a better time, this is clearly not the best time and people are not gonna join because there's only 3 contestants, unless by magic or by interest people pop in.